Hybrid three-dimensional woven/laminated struts for composite structural applications

ABSTRACT

A woven preform used to reinforce a composite structure which includes a central portion having a plurality of inter-woven layers. The preform also includes first and second end portions having a plurality of independent woven layers that are integrally woven with the plurality of interwoven layers in the central portion and which extend along the entire length the preform. Interspersed between the plurality of independent woven layers in the first and second end portions are bias plies.

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 7,655,581. The reissue application are application Ser.Nos. 13/385,114 (now U.S. Pat. No. Re. 45,777) and 13/385,113 (thepresent application).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The instant invention relates to the geometrical configuration ofthree-dimensional woven preforms for reinforced composite structureshaving quasi-isotropic or multi-directional reinforcement on one or twoends of the structure and approximately unidirectional reinforcement inall other areas.

2. Background of the Invention

The use of reinforced composite materials to produce structuralcomponents is now widespread, particularly in applications where theirdesirable characteristics for being lightweight, strong, tough,thermally resistant, self-supporting and adaptability to being formedand shaped are sought. Such components are used, for example, in theaeronautical, aerospace, satellite, and battery industries, as well asfor recreational uses such as in racing boats and autos, and incountless other applications. A three-dimensional fabric generallyconsists of fibers oriented in three directions with each fiberextending along a direction perpendicular to the other fibers, that isalong the X, Y and Z axial directions.

Typically, components formed from such fabrics consist of reinforcementmaterials embedded in matrix materials. The reinforcement component maybe made from materials such as glass, carbon, ceramic, aramid (e.g.,“KEVLAR®”), polyethylene, and/or other materials which exhibit desiredphysical, thermal, chemical and/or other properties, chief among whichis great strength against stress failure. Through the use of suchreinforcement materials, which ultimately become a constituent elementof the completed component, the desired characteristics of thereinforcement materials such as very high strength, are imparted to thecompleted composite component. The constituent reinforcement materialsmay typically be woven, knitted or otherwise oriented into desiredconfigurations and shapes for reinforcement preforms. Usually,particular attention is paid to ensure the optimum utilization of theproperties for which these constituent reinforcing materials have beenselected. Generally, such reinforcement preforms are combined withmatrix material to form desired finished components or produce workingstock for the ultimate production of finished components.

After a desired reinforcement preform has been constructed, matrixmaterial may be introduced and combined with the preform, so that thereinforcement preform becomes encased in the matrix material such thatthe matrix material fills the interstitial areas between the constituentelements of the reinforcement preform. The matrix material may be any ofa wide variety of materials, such as epoxy, polyester, vinyl-ester,ceramic, carbon and/or other materials, which also exhibit desiredphysical, thermal, chemical and/or other properties. The materialschosen for use as the matrix may or may not be the same as that of thereinforcement preform and may or may not have comparable physical,chemical thermal or other properties. Typically, however, they will notbe of the same materials or have comparable physical, chemical, thermalor other properties, as the reinforcement preform, since a usualobjective sought in using composites in the first place is to achieve acombination of characteristics in the finished product that is notattainable through the use of one constituent material alone.

When combined, the reinforcement preform and the matrix material maythen be cured and stabilized in the same operation by thermosetting orother known methods, and then subjected to other operations towardproducing the desired component. It is significant to note that afterbeing so cured, the then solidified masses of the matrix material arenormally very strongly adhered to the reinforcing material (e.g., thereinforcement preform). As a result, stress on the finished component,particularly via its matrix material acting as an adhesive betweenfibers, may be effectively transferred to and borne by the constituentmaterial of the reinforcing reinforcement preform.

Typically, simple, two-dimensional woven fabrics or uni-directionalfibers are produced by a material supplier and sent to a customer whocuts out patterns and lays up the final part ply-by-ply. The simplestwoven materials are flat, substantially two-dimensional structures withfibers in only two directions. They are formed by interlacing two setsof yarns perpendicular to each other. In two-dimensional weaving, the 0°yarns are called warp fibers or yarns and the 90° yarns are called theweft or fill fibers or yarns. For resin transfer molding, a series ofwoven fabrics can be combined to form a dry lay-up, which is placed in amold and injected with resin. These fabrics can be pre-formed usingeither a “cut and sew” technique or thermally formed and “tacked” usinga resin binder.

Two-dimensional woven structures, however, have limitations. The step ofpre-forming requires extensive manual labor in the lay-up.Two-dimensional woven structures are not as strong or stretch-resistantalong other than the 0° and 90° axes, particularly at angles fartherfrom the fiber axes. One method to reduce this possible limitation is toadd bias fibers to the weave, fibers woven to cut across the fabric atan intermediate angle, preferably at ±45° to the axis of the fillfibers.

Simple woven preforms are also single layered. This limits the possiblestrength of the material. One possible solution is to increase the fibersize. Another is to use multiple layers, or plies. An additionaladvantage of using multiple layers is that some layers may be orientedsuch that the warp and weft axes of different layers are in differentdirections, thereby acting like the previously discussed bias fibers. Ifthese layers are a stack of single layers laminated together with theresin, however, then the problem of de-lamination arises. If the layersare sewn together, then many of the woven fibers may be damaged duringthe sewing process and the overall tensile strength may suffer. Inaddition, for both lamination and sewing of multiple plies, a handlay-up operation usually is necessary to align the layers.Alternatively, the layers may be interwoven as part of the weavingprocess. Creating multiple interwoven layers of fabric, particularlywith integral bias fibers, has been a difficult problem.

One example of where composite materials are used to produce structuralcomponents is in the production of struts and braces. Struts and bracestypically comprise a central column having lugs on each end of thestructure. These lugs can have either male or female (clevis)configurations and are used to attach the strut or brace to thestructure it is reinforcing or bracing. As previously discussed, inorder to achieve increased strength of the composite structure, multiplelayers or plies are used for the lug and column portions of the strutsand braces. Although using multiple layers is advantageous sinceindividual layers can be oriented to provide reinforcement in the 0° and90° directions as well as can be oriented on the bias to providereinforcement in additional directions, such as the ±45° directions, iflaminated together with resin, delamination of the layers may beproblematic. Alternatively, if the layers are sewn together, then aspreviously discussed, many of the woven fibers may be damaged during thesewing process, reducing the overall tensile strength of the finalstructure.

Many examples of laminated lugs exist, some using hybrid materials (i.e.alternating carbon and titanium plies), but the laminated lugs have notbeen combined with a three-dimensional woven column. The viability oflaminated composite lugs for very highly loaded structures has beendemonstrated in several government funded programs. However, to theApplicant's knowledge, none of these programs considered the use ofthree-dimensional woven preforms.

Thus, three-dimensional preforms for use in struts and braces, havinglaminated lug ends or portions and a monolithic three-dimensional wovencentral column are desirable. The advantages of using athree-dimensional construction in the central portion of the preform arethat it reduces the labor required to cut and collate all of the pliesrequired for a thick composite, and it provides better damage tolerancethan conventional laminated composites. The advantage of the independentlayers in the ends is that the laminate can be tailored to have specificproperties.

Accordingly, a need exists for a woven preform having an integrallywoven three-dimensional central portion with laminated lug endscomprised of independent, woven layers.

SUMMARY OF THE INVENTION

It is therefore a principal object of the invention to provide athree-dimensional woven preform having an interwoven column portion anda stack of individually woven fabrics at the lug ends for use in acomposite structure.

It is a further object of the invention to provide a woven preform for athick composite structure that has quasi-isotropic or multi-directionalreinforcement on one or two ends and nearly unidirectional reinforcementin all areas.

Yet another object of the invention is to provide a composite structurethat can be used to carry large concentrated loads.

These and other objects and advantages are provided by the instantinvention. In this regard, the instant invention is directed to a wovenpreform that is used to reinforce a composite structure and a method ofmanufacturing such a preform. The woven preform comprises a centralportion with a plurality of layers woven together. The preform includesa first end portion having a plurality of independently woven layersthat are integrally woven with the plurality of interwoven layers in thecentral portion and which extend along the entire length of the preform.The preform also includes a second end portion having a plurality ofindependently woven layers that are integrally woven with the pluralityof interwoven layers in the central portion and which extend along theentire length of the preform. Interspersed between the plurality ofindependently woven layers in the first and second end portions are biasplies. In order to provide gaps between the independently woven layersin the first and second end portions for the bias plies, layers of warpfibers or yarns are woven out of the preform. In addition, a wovenpreform having a single lug end and a column portion end can beconstructed according to any of the disclosed embodiments.

Another aspect of the instant invention is directed to athree-dimensional reinforced composite structure constructed using awoven preform disclosed herein. The reinforced composite structurecomprises a central portion that has unidirectional reinforcement andfirst and second end portions that are quasi-isotropically ormulti-directionally reinforced. The reinforced composite structure mayalso be constructed to have a column portion at one end and a lugportion at the other end.

The various features of novelty which characterize the invention arepointed out in particularity in the claims annexed to and forming a partof this disclosure. For a better understanding of the invention, itsoperating advantages and specific objects attained by its uses,reference is made to the accompanying descriptive matter in whichpreferred embodiments of the invention are illustrated in theaccompanying drawings in which corresponding components are identifiedby the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the present invention solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1 is a plan view of a composite structure having a column portionwith lug ends having a male configuration;

FIG. 2 is a plan view of a composite structure having a column portionwith lug ends having a female or clevis configuration;

FIG. 3 is a plan view of a preform constructed according to oneembodiment of the instant invention;

FIG. 4A is a plan view of a preform having lug ends with a symmetricalconfiguration constructed according to one embodiment of the instantinvention;

FIG. 4B is a plan view of a preform having lug ends with a symmetricalconfiguration constructed according to one embodiment of the instantinvention;

FIG. 4C is a plan view of a preform having lug ends with an asymmetricalconfiguration constructed according to one embodiment of the instantinvention;

FIG. 4D is a plan view of a preform having lug ends with an asymmetricalconfiguration constructed according to one embodiment of the instantinvention; and

FIG. 5 is a plan view of a preform constructed according to oneembodiment of the instant invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The instant invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theillustrated embodiments set forth herein. Rather, these illustratedembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art.

In the following description, like reference characters designate likeor corresponding parts throughout the figures. Additionally, in thefollowing description, it is understood that such terms as “upper,”“lower,” “top” and “bottom” and the like are words of convenience andare not to be construed as limiting terms.

The instant invention is a preform concept for a composite structure orbeam that has quasi-isotropic or multi-directional reinforcement on oneor two ends and nearly unidirectional reinforcement in all other areas.This configuration is desirable for structures that have to carry largeconcentrated loads, such as struts and braces. The quasi-isotropic ormulti-directionally reinforced ends provide good bearing properties andmore balanced tension, compression, and shear strengths, making themgood choices for the lug ends of the structure. These lug ends can haveeither male or female (clevis) configurations. The unidirectionalportion provides high axial stiffness, which is good for preventingcolumn buckling or crippling, making it a good choice for the maincolumn of a strut or brace. Depicted in FIG. 1 is a strut or brace 2having lug ends 4 and a three-dimensional main column portion 6. The lugends 4 in FIG. 1 have a male configuration. FIG. 2 depicts a strut orbrace 8 with a three-dimensional main column portion 10 and lug ends 12having a female or clevis configuration.

The advantages of using a three-dimensional construction in the centralportion of the preform are that it reduces the labor required to cut andcollate all of the plies required for a thick composite and it providesbetter damage tolerance than conventional laminated composites. Theadvantage of the independent layers at the ends of the structure is thatthe laminate can be tailored to have specific properties. As disclosed,the lug ends are considered to be quasi-isotropic or multi-directionallyreinforced, but they could be practically any laminate configuration.

The instant preform is comprised of a three-dimensional woven portionconsisting of a number of layers and a similar number of independentbias layers. In the central or column portion of the three-dimensionalwoven piece, all of the layers are interwoven or integrally woventogether forming a monolithic block of woven material. The fiberarchitecture used in this portion can be any conventional pattern for athick preform, including, but not limited to, ply-to-ply, throughthickness, angle interlock, or orthogonal architectures. At the ends ofthe structure, the individual layers weave independent of one another toform a stack of fabrics with reinforcement in the 0° and 90° directions,where 0° is along the length of the structure. The bias layers or plies,which are separately constructed provide reinforcement in additionaldirections to the 0°/90° direction such as in the ±45° direction, areinterspersed between the layers of 0°/90° fabrics to form a moreconventional laminate. The bias layers or plies can be woven using warpand weft fibers or yarns or they can be nonwoven, knitted or an array ofMD or CD fibers or yarns. In the following figures, the warp directionis along the 0° direction or along the length of the structure and isindicated by arrow 100.

All of the layers that comprise the preform, including the central orcolumn portion, are woven with warp fibers or yarns and weft or fillfibers or yarns using a Jacquard loom and captured shuttle, however, anyconventional weaving technique may be used to weave the layers. Thefibers or yarns can be either synthetic or natural materials such as,but not limited to carbon, nylon, rayon, polyester, fiberglass, cotton,glass, ceramic, aramid (“KEVLAR®”) and polyethylene. The completed wovenpreform is then processed into a woven/laminated composite structurewith the introduction of a matrix material such as, but not limited to,epoxy, polyester, vinyl-ester, ceramic, carbon and/or other materials,which also exhibit desired physical, thermal, chemical and/or otherproperties, using conventional techniques such as, but not limited to,resin transfer molding or chemical vapor infiltration.

According to one embodiment of the instant invention, FIG. 3 depicts asegment of a structure 14 having a thick central portion 16 that isintegral with two thinner male lug ends 18 that are positioned on eachside of central portion 16. As can be seen FIG. 3, the thick centralportion 16 is a monolithic, three-dimensional woven column comprised ofa plurality of woven layers 20 that are interwoven or woven together. Inorder to form the thinner male lug ends 18, layers of warp fibers fromthe thick central column 16 are woven out of the preform to provide atapered transition 22 from the column 16 to the thinner lug ends 18.

Once the desired number of warp fiber layers are woven out of thepreform to taper the column down to the desired lug thickness,additional layers of warp fibers are woven out of the preform at thethinner lug ends 18 to provide a gap or space for the bias fabric plies.The remaining warp fibers at the thinner lug ends 18, which areintegrally woven with the plurality of layers 20 in the column orcentral portion 16 and are continuous along the length of the structure,form individual layers of plies 24 that are woven independently of oneanother. This stack of plies or fabrics provide reinforcement at thethinner lug ends 18 in the 0° and 90° directions. Since the 0°/90° plies24 are not interwoven with each other, bias plies 26 that providereinforcement in additional directions, such as the ±45° direction, canbe interspersed in the gaps between the 0°/90° plies 24, forming a stackof fabrics that, when a matrix material is applied, forms a laminatedstructure that provides quasi-isotropic or multi-directionalreinforcement at the thinner lug ends 18. Furthermore, as depicted inFIG. 3, the structure has a continuous surface fiber 28 that is theresult of the outermost warp fibers of the thick column 16.

If so desired, unlike the previously disclosed structure for thisembodiment that has a central portion 16 with two thinner lug ends 18 oneach side of the central portion 16, a structure having only one thinnerlug end 18 may be constructed according to the disclosed embodiment. Insuch a case, the structure will comprise one end similar to themonolithic, three-dimensional woven central portion 16 and one thinnerlug end 18 as disclosed above. A structure constructed in this manner,will more closely resemble FIG. 3.

Another embodiment of the instant invention is depicted in FIGS. 4A-4D,which show a segment of a structure 30 comprising two lug ends 32 thatare thicker than the monolithic three-dimensional woven central columnportion 34 of the structure 30. As is the case in the previousembodiment, the central column portion 34 is comprised of a plurality ofwoven layers 35 that are interwoven or woven together. In thisconfiguration, however, there is no need to weave out warp fibers 36from the column portion 34 in order to form the thicker lug ends 32.Instead, all of the warp fibers 36 used to construct the column portion34 are used to construct the thicker lug ends 32. The warp fibers 36from the column portion 24, however, are not interwoven with each otherat the thicker lug ends 32. This allows the bias plies 38 to beinterspersed between the warp fibers 40 in the thicker lug ends 32,which are the plies that provide reinforcement in the 0°/90° direction.Therefore, the thicker lug ends 32 have a stack of fabrics consisting of0°/90° oriented plies or fabrics and separately constructed pliesoriented in directions other than the 0°/90° direction, for example ±45°oriented plies or fabrics that, when a matrix material is applied,results in a laminated lug having quasi-isotropic or multi-directionalreinforcement. Furthermore, as can be seen in FIGS. 4A-4D, structuresconstructed according to this embodiment will have a staggeredtransition 42 from the laminated thicker lug end 32 to the monolithiccolumn portion 34, thereby improving load transfer from one portion tothe other.

As can be seen in FIGS. 4A-4D, the length and positioning of the biasplies 38 varies from figure to figure. FIGS. 4A and 4B depict a lug end32 having a symmetrical configuration. That is, the length andpositioning of the bias plies 38 in the lug end 32 are symmetric aboutthe center line or longitudinal axis A-A. FIG. 4A depicts a symmetricalconfiguration where the length of successive bias plies 38 increases inthe upper half 39 and the lower half 41 of the lug end 32 as one movesfrom the center line A-A toward the top surface 43 and the bottomsurface 45 of the lug end 32. FIG. 4B depicts a symmetricalconfiguration where the length of successive bias plies 38 decreases inboth halves, 39 and 41, of the lug end 32 as one moves from the centerline A-A toward the top surface 43 and the bottom surface 45 of the lugend 32.

FIGS. 4C and 4D depict a lug end 32 having an asymmetricalconfiguration. That is, the length of the successive bias plies 38 inthe lug end 32 only increases or decreases as one moves from the bottomsurface 45 to the top surface 43 of the lug end 32. FIG. 4C shows anasymmetrical configuration where the length of successive bias plies 38in the lug end 32 increases as one moves from the bottom surface 45 tothe top surface 43 of the lug end 32. As shown in FIG. 4D, anasymmetrical lug end 32 can also be constructed where the length ofsuccessive bias plies 38 decreases as one moves from the bottom surface45 to the top surface 43 of the lug end 32.

If so desired, unlike the previously disclosed structures for thisembodiment that have a central portion 34 with two thicker lug ends 32on each side of the central portion 34, a structure having only onethicker lug end 32 may be constructed according to the disclosedembodiment. In such a case, the structure will comprise one end similarto the monolithic, three-dimensional woven central portion 34 and onethicker lug end 32 as disclosed above. A structure constructed in thismanner, will more closely resemble the structures depicted in FIGS.4A-4D.

In another embodiment of the instant invention, FIG. 5 depicts a segmentof a structure 44 having a monolithic three-dimensional woven centralcolumn portion 46 with two female lugs or devises 48. As can be seen inFIG. 5, the female lug ends 48 are angled relative to the central columnportion 46, such that the female lug ends 48 are not in line orcollinear with central column portion 46. Similarly to the previousembodiments, the central column portion 46 is comprised of a pluralityof woven layers 50 that are interwoven or woven together. In order toform the female lug ends or devises 48, the monolithic column portion 46is woven such that it bifurcates 52 to form both halves of the devises.The 0°/90° layers 54 in the first or angled portion 56 of each half ofthe devises continue to be interwoven together.

In order to provide a gap between the 0°/90° reinforcing layers 58 forthe bias fabric plies 60 in the parallel or end portions 62 of theclevis, warp fibers are woven out of the angled portions 56 of thepreform. The remaining warp fibers at the lug ends 48, which areintegrally woven with the plurality of woven layers 50 in the centralcolumn portion 46 and angled portions 54, form individual layers thatare woven independently of one another and provide reinforcement at theclevis 48 in the 0° and 90° directions. Since the 0°/90° layers 58 arenot interwoven with each other, reinforcement in directions other thanthe 0°/90° direction, for example the ±45° direction is provided by thebias plies 60 that are interspersed between the 0°/90° plies 58, formingstacks of fabric at the devises that provide quasi-isotropic ormulti-directional reinforcement when a matrix material is added to thepreform.

If so desired, unlike the previously disclosed structure for thisembodiment that has a central portion 46 with two female lug ends ordevises 48 on each side of the central portion 46, a structure havingonly one female lug end 48 may be constructed according to the disclosedembodiment. In such a case, the structure will comprise one end similarto the monolithic, three-dimensional woven central portion 46 and onefemale lug end or clevis 48 as disclosed above. A structure constructedin this manner, will more closely resemble the structure depicted inFIG. 5.

In all of the disclosed embodiments, after the bias plies are insertedat the lug ends, the woven preform can be over-braided with a ply ofglass material in order to improve the preform's abrasion resistance.

As is apparent to those skilled in the art, the structures disclosedabove can have many forms in addition to those disclosed herein. Forexample, the structures can have a thick monolithic three-dimensionalwoven column with female or clevis lug configurations. The structure canalso have a thick monolithic three-dimensional woven column with a malelug on one end and a female lug at the other end. In addition, thestructure can have a thin monolithic three-dimensional woven column withfemale lugs at each end or a male lug at one end and a female lug at theother end. Lastly, all configurations can have: both lugs in line withor collinear with the main column portion; both lugs angled relative tothe main column portion; or one lug can be collinear with the mainportion and one lug can be angled relative to the main portion. Althoughas disclosed above, the lug ends are considered to be quasi-isotropic ormulti-directionally reinforced, the lug ends can be practically anylaminate configuration. Therefore, the instant structures, for example astrut or brace, can be designed to have different configurations inorder to provide various types of reinforcing or bracing based on astructure's specific need or desired use.

Although a preferred embodiment of the present invention andmodifications thereof have been described in detail herein, it is to beunderstood that this invention is not limited to this precise embodimentand modifications, and that other modifications and variations may beeffected by one skilled in the art without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A woven preform used to reinforce a compositestructure comprising: a central portion having a plurality of interwovenlayers; a first end portion having a plurality of independent wovenlayers; a second end portion having said plurality of independent wovenlayers; wherein plies of said plurality of independent woven layersextend through the entire length of said preform wherein said plies areintegrally woven in said central portion to form a three dimensionalfabric construction; and wherein said plies are independently woven insaid end portions to form a stack of woven fabric; wherein bias pliesare interspersed between said plurality of independent woven layersplies in said first and second end portions.
 2. The woven preform asclaimed in claim 1, wherein said central portion comprises a pluralityof layers that extend long the entire length of said woven preform and aplurality of layers that partially extend along the length of said wovenpreform.
 3. The woven preform as claimed in claim 2, wherein saidpartially extending layers are formed by warp fibers or yarns that weaveout of said woven preform and provide a transition from said centralportion to said first and second end portions.
 4. The woven preform asclaimed in claim 2, wherein gaps for said bias plies between saidindependent woven layers in said first and second end portions are aresult of warp fibers or yarns that weave out of said woven preform. 5.The woven preform as claimed in claim 1, wherein said first end portionis a lug having a male or a female configuration.
 6. The woven preformas claimed in claim 1, wherein said second end portion is a lug having amale or a female configuration.
 7. The woven preform as claimed in claim1, wherein said first end portion is collinear with or angled relativeto said central portion.
 8. The woven preform as claimed in claim 1,wherein said second end portion is collinear with or angled relative tosaid central portion.
 9. The woven preform as claimed in claim 3,wherein said transition between said column portion and said first andsecond end portions is a smooth tapered transition or a staggeredtransition.
 10. The woven preform as claimed in claim 1, wherein saidcentral portion is bifurcated at an end of said central portion.
 11. Thewoven preform as claimed in claim 10, wherein said bifurcated end formstwo halves of a female lug or clevis.
 12. The woven preform as claimedin claim 1, wherein said central portion is thicker than said first andsecond end portions.
 13. The woven preform as claimed in claim 1,wherein said central portion is thinner than said first and second endportions.
 14. The woven preform as claimed in claim 1, wherein saidfirst end portion and said second end portion are woven with warp andweft fibers or yarns.
 15. The woven preform as claimed in claim 1,wherein said layers in said central portion are woven layers woven withwarp and weft fibers or yarns.
 16. The woven preform as claimed in claim1, wherein said central portion has a fiber architecture selected fromthe group consisting of ply-to-ply, through thickness, orthogonal, andangle interlock.
 17. The woven preform as claimed in claim 14 or 15,wherein said warp and weft fibers or yarns are selected from the groupof synthetic or natural materials consisting of carbon, nylon, rayon,polyester, fiberglass, cotton, glass, ceramic, aramid, and polyethylene.18. The woven preform as claimed in claim 1, wherein said woven preformis overbraided with a ply of glass.
 19. A method of manufacturing awoven preform used to reinforce a composite structure comprising thesteps of: weaving a plurality of layers together to form a monolithiccentral portion; weaving a plurality of independent layers to form afirst end portion; weaving said plurality of independent layers to forma second end portion, wherein plies of said plurality of independentwoven layers extends through the entire length of said preform, whereinsaid plies are integrally woven in said central portion to form a threedimensional fabric construction, and wherein said plies areindependently woven in said end portions to form a stack of wovenfabric; and interspersing bias plies between said plurality ofindependent woven plies in said first and said second end portions. 20.The method as claimed in claim 19 further comprising the step of weavingwarp fibers or yarns out of said woven preform in order to provide atransition from said central portion to said first and second endportions.
 21. The method as claimed in claim 19 further comprising thestep of weaving warp fibers or yarns out of said woven preform to formindependent woven layers in said first and second end portions therebyproviding a gap between said independent woven layers for said biasplies.
 22. The method as claimed in claim 19, wherein said first endportion is a lug having a male or a female configuration.
 23. The methodas claimed in claim 19, wherein said second end portion is a lug havinga male or a female configuration.
 24. The method as claimed in claim 19,wherein said first end portion is collinear with or angled relative tosaid central portion.
 25. The method as claimed in claim 19, whereinsaid second end portion is collinear with or angled relative to saidcentral portion.
 26. The method as claimed in claim 20, wherein saidtransition between said column portion and said first and second endportions is a smooth tapered transition or a staggered transition. 27.The method as claimed in claim 19, wherein said central portion is wovento have bifurcation at an end of said central portion.
 28. The method asclaimed in claim 27 wherein said bifurcated end forms two halves of afemale lug or clevis.
 29. The method as claimed in claim 19, whereinsaid central portion is thicker than said first and second end portions.30. The method as claimed in claim 19, wherein said central portion isthinner than said first and second end portions.
 31. The method asclaimed in claim 19, wherein said central portion, said first endportion and said second end portion are woven with warp and weft fibersor yarns.
 32. The method as claimed in claim 19, wherein said centralportion is woven with a fiber architecture selected from the groupconsisting of ply-to-ply, through thickness, orthogonal, and angleinterlock.
 33. The method as claimed in claim 19, wherein said warp andweft fibers or yarns are selected from the group of synthetic or naturalmaterials consisting of carbon, nylon, rayon, polyester, fiberglass,cotton, glass, ceramic, aramid, and polyethylene.
 34. The method asclaimed in claim 19, wherein said woven preform is overbraided with aply of glass.
 35. A three-dimensional composite structure reinforcedwith a woven preform comprising: a central portion having a plurality ofinterwoven layers; a first end portion having a plurality of independentwoven layers; a second end portion having said plurality of independentwoven layers; wherein plies of said plurality of independent wovenlayers extend through the entire length of said preform wherein saidplies are integrally woven in said central portion to form a threedimensional fabric construction; and wherein said plies areindependently woven in said end portions to form a stack of wovenfabric; wherein bias plies are interspersed between said plurality ofindependent woven layers plies in said first and second end portions;and a matrix material.
 36. The composite structure as claimed in claim35, wherein said central portion comprises a plurality of layers thatextend along the entire length of said woven preform and a plurality oflayers that partially extend along the length of said woven preform. 37.The composite structure as claimed in claim 36, wherein said partiallyextending layers are formed by warp fibers or yarns that weave out ofsaid woven preform and provide a transition from said central portion tosaid first and second end portions.
 38. The composite structure asclaimed in claim 36, wherein gaps for said bias plies between saidindependent woven layers in said first and second end portions are aresult of warp fibers or yarns that weave out of said woven preform. 39.The composite structure as claimed in claim 35, wherein said first endportion is a lug having a male or a female configuration.
 40. Thecomposite structure as claimed in claim 35, wherein said second endportion is a lug having a male or a female configuration.
 41. Thecomposite structure as claimed in claim 35, wherein said first endportion is collinear with or angled relative to said central portion.42. The composite structure as claimed in claim 35, wherein said secondend portion is collinear with or angled relative to said centralportion.
 43. The composite structure as claimed in claim 37, whereinsaid transition between said column portion and said first and secondend portions is a smooth tapered transition or a staggered transition.44. The composite structure as claimed in claim 35, wherein said centralportion is bifurcated at an end of said central portion.
 45. Thecomposite structure as claimed in claim 44, wherein said bifurcated endforms two halves of a female lug or clevis.
 46. The composite structureas claimed in claim 35, wherein said central portion is thicker thansaid first and second end portions.
 47. The composite structure asclaimed in claim 35, wherein said central portion is thinner than saidfirst and second end portions.
 48. The composite structure as claimed inclaim 35, wherein said first and said second end portions arequasi-isotropically or multi-directionally reinforced.
 49. The compositestructure as claimed in claim 35, wherein said first end portion andsaid second end portion are woven with warp and weft fibers or yarns.50. The composite structure as claimed in claim 35, wherein said layersin said central portion are woven layers woven with warp and weft fibersor yarns.
 51. The composite structure as claimed in claim 35, whereinsaid woven central portion has a fiber architecture selected from thegroup consisting of ply-to-ply, through thickness, orthogonal, and angleinterlock.
 52. The composite structure as claimed in claim 49 or 50,wherein said warp and weft fibers or yarns are selected from the groupof synthetic or natural materials consisting of carbon, nylon, rayon,polyester, fiberglass, cotton, glass, ceramic, aramid, and polyethylene.53. The composite structure as claimed in claim 36, wherein saidcomposite structure is formed from a process selected from the groupconsisting of resin transfer molding and chemical vapor filtration. 54.The composite structure as claimed in claim 53, wherein said matrixmaterial is selected from the group consisting of epoxy, polyester,vinyl-ester, ceramic, and carbon.
 55. A woven preform used to reinforcea composite structure comprising: a column portion having a plurality ofinterwoven layers; and a lug end portion having a plurality ofindependent woven layers, wherein plies of said plurality of independentwoven layers extend through the entire length of said preform whereinsaid plies are integrally woven in said column portion to form a threedimensional fabric construction; and wherein said plies areindependently woven in said end portion to form a stack of woven fabric;wherein bias plies are interspersed between said plurality ofindependent woven layers plies in said lug end portion.
 56. The wovenpreform as claimed in claim 55, wherein said lug end portion has a maleor female configuration.
 57. The woven preform as claimed in claim 55,wherein said lug end portion is collinear with or angled relative tosaid column portion.
 58. The woven preform as claimed in claim 55,wherein said column portion is thicker than said lug end portion. 59.The woven preform as claimed in claim 55, wherein said column portion isthinner than said lug end portion.
 60. The woven preform as claimed inclaim 55, further comprising a matrix material.
 61. A woven preform foruse as reinforcement in a composite structure comprising: athree-dimensional central portion having a plurality of warp fibersinterwoven with a plurality of weft fibers in three dimensions (X, Y,and Z); a first end portion; and a second end portion; wherein saidwoven preform comprises one or more warp fibers on an outer surface ofsaid preform that extend continuously on the outer surface along theentire length of said woven preform; and wherein said woven preformcomprises one or more warp fibers that extend along the entire length ofsaid woven preform and a plurality of warp fibers that weave out of saidwoven preform and provide a transition from said central portion to atleast one of said first and second end portions.
 62. A method ofmanufacturing a woven preform for use as reinforcement in a compositestructure comprising the steps of: weaving a plurality of warp fiberswith a plurality of weft fibers in three dimensions (X, Y, and Z) toform a three-dimensional central portion; weaving a plurality of thewarp fibers with a plurality of weft fibers in three dimensions (X, Y,and Z) to form a three-dimensional first end portion; weaving aplurality of the warp fibers with a plurality of weft fibers in threedimensions (X, Y, and Z) to form a three-dimensional second end portion;wherein the woven preform comprises one or more warp fibers on an outersurface of said woven preform are woven to extend along the entirelength of said woven preform; and wherein said woven preform comprisesone or more warp fibers that extend continuously on outer surface alongthe entire length of said woven preform and a plurality of warp fibersthat weave out of said woven preform and provide a transition from saidcentral portion to at least one of said first and second end portions.63. A woven preform for use as reinforcement in a composite structurecomprising: a three-dimensional central portion having a plurality ofwarp fibers interwoven with a plurality of weft fibers in threedimensions (X, Y, and Z); and wherein said woven preform comprises oneor more warp fibers on an outer surface of said woven preform thatextend continuously on the outer surface along the entire length of saidwoven preform; and wherein two or more warp fibers in adjacent layersexchange position through a thickness of the central portion at abifurcation at an end of said central portion.
 64. A method ofmanufacturing a woven preform for use as reinforcement in a compositestructure comprising the step of: weaving a plurality of warp fiberswith a plurality of weft fibers in three dimensions (X, Y, and Z) toform a three-dimensional central portion of the woven preform such thatone or more warp fibers extend continuously on an outer surface of thethree-dimensional central portion of the preform and extend along theentire length of said woven preform; wherein two or more warp fibers inadjacent layers of the central portion are woven to exchange positionthrough a thickness of the central portion at a bifurcation at an end ofsaid central portion.
 65. A woven preform for use as reinforcement in acomposite structure comprising: at least one end portion; and athree-dimensionally woven central portion comprising a plurality of warpfibers interwoven with a plurality of weft fibers in three dimensions(X, Y, and Z) comprising: the plurality of weft fibers comprising firstyarns extending in a weft direction; the plurality of warp fiberscomprising second yarns extending in a warp direction, wherein the firstand second yarns form interwoven layers in the central portion; whereinthere is a greater number of second yarns in a first region of the wovencentral portion than in a second region of the woven central portion.66. A method of forming a woven preform comprising a three-dimensionallywoven central portion and at least one end portion for use asreinforcement in a composite structure comprising the steps of: weavingfirst yarns extending in a weft direction and second yarns extending ina warp direction to form the three-dimensionally woven central portionat a first region of the preform; weaving out select second yarns inthree dimensions (X, Y, and Z) in a second region of the preform toreduce a thickness of the three-dimensionally woven central portion inthe second region.
 67. A woven preform for use as reinforcement in acomposite structure comprising: at least one end portion; and athree-dimensionally woven central portion comprising a plurality of warpyarns interwoven with a plurality of weft yarns in three dimensions (X,Y, and Z), wherein one or more warp yarns extend along the entire lengthof said preform, and one or more warp yarns extend less than the entirelength of said preform.